EP1947386B1 - Turbulator, in particular for a boiler with smoke pipes, and corresponding boiler - Google Patents

Description

The invention relates to a turbulator, particularly for a flue gas boiler, a boiler and a corresponding manufacturing method.

Smoke tube boilers are particularly used for installations requiring a high flow rate. A boiler of this type is represented in figure 1 .

These boilers 1 comprise a combustion chamber 2 equipped with a burner 3, inside which the combustion gases are burned and produce fumes.

Tubes 4, arranged vertically in this example, open at one end into the combustion chamber 2 and at the other end into a discharge chamber 5, connected to a chimney 6.

The boiler further comprises a volume of water to be heated 7, in contact with the outer wall of the tubes 4. The water from the installation enters at the lower part 8 and, after heating, is expelled at the level of the upper part 9.

The walls of the tubes thus form heat exchangers, the length and the amount of tubes 4 influencing the performance of the boiler.

A disadvantage arises because of the laminar flow of the fumes from the combustion chamber inside the tubes, or laminar boundary layers appearing in turbulent regime.

Indeed, in both cases, the fumes flow in the longitudinal direction of the tube forming separate veins.

Thus, only the fumes in contact with the inner wall of the tube participate in the heat exchange and cool, unlike hot fumes flowing in the vein or central zone of the tube.

Consequently, the efficiency of the boiler remains low in laminar flow and the fumes to be evacuated have a very high temperature.

In this case, it is necessary to increase the length or the number of tubes in order to improve the performance of the boiler. It is also necessary to provide a suitable evacuation device, so as to withstand the high temperatures of the fumes.

In order to overcome these disadvantages, it is known to use turbulators arranged inside the tubes, so as to avoid laminar flow.

Turbulators are described in the documents US 1,632,888 and US 4,412,558 . These are in the form of a folded plate comprising a succession of contiguous slats constituting a zig-zag shape.

This type of turbulator has, in top view, a generally rectangular shape so that, once inserted into the cylindrical tube, the spaces between the edges of the turbulator and the tube can constitute laminar flow zones, which affects boiler performance as seen previously.

The document US 2,067,133 discloses a turbulator having a general shape with two helices nested one inside the other, each helix being made by a succession of flat slats inclined relative to each other.

This turbulator has, between the lamellae of each of the propellers, openings allowing the passage of the fluid in the center of the tube, the particular form of the turbulator for stirring the fluid without creating significant pressure drops.

The performance of such a turbulator, however, remains limited.

The invention aims to remedy these drawbacks by proposing a turbulator providing maximum boiler efficiency.

For this purpose, the invention relates to a turbulator, in particular for a flue gas boiler in which the fumes circulate in each tube from one end to another, the turbulator being intended to be arranged in a tube and constituted by an element. elongate blade-shaped having a succession of contiguous slats and having a zig-zag shape, characterized in that the slats have a median zone of greater width than their ends and have rounded convex edges.

The turbulator thus has, in top view, a rounded shape adapted to the shape of the tube. The space between the edges of the turbulator and the tube can then be considerably reduced.

The turbulator according to the invention affects the smoke over most of the section of the tube so as to create a large stirring. This causes a homogenization of the temperature over the entire section of the tube and avoids any laminar flow may cause the presence of hot veins.

Advantageously, the respective widths of the median zone of two successive lamellae increase in the direction of circulation of the fumes.

Because of the heat exchanges occurring inside the tube, the temperature of the fumes in the upper part of the tube, coming from the combustion chamber, is very important. This temperature is lowered at the bottom of the tube.

At a constant flow rate, due to the expansion of the gases at high temperature, the smoke velocity is higher in the upper part than in the lower part of the tube.

The pressure loss generated is increasing with the speed of the fumes, it is very important in the upper part of the tube.

This necessarily results in oversizing of the injection means of the combustion gases.

The reduced width of the central zone in the upper part of the tube makes it possible to reduce the pressure losses created in this part of the tube.

In addition, the efficiency of the turbulator in the upper part of the tube is not substantially affected by the reduced section of the turbulator. Indeed, because of the high speeds of the fumes in this area, a turbulent regime is easily established and does not require a large deflection section, as is the case in the lower part.

In addition, because of the low smoke velocity at the bottom, a large section of the turbulator does not cause a consequent increase in the pressure drop.

Preferably, the lamellae are substantially flat.

Advantageously, the connection zones between two successive lamellae are arranged perpendicularly to the longitudinal direction of the turbulator.

According to a possibility of the invention, the angle formed between two successive lamellae is between 90 and 135 °, preferably of the order of 120 °.

This interval offers a good compromise between the amount of material needed to produce a turbulator and the efficiency of the latter.

Preferably, the lamella of the turbulator located upstream in the flue gas flow direction has a maximum width of between 55 and 85% of the inside diameter of the tube.

Advantageously, the lamella of the turbulator located downstream in the flue gas flow direction has a maximum width of between 80 and 95% of the inside diameter of the tube.

The invention further relates to a boiler with flue tubes, characterized in that it comprises at least one turbulator according to the invention, inserted into at least one flue tube.

• découpage de la feuille de manière à définir les contours des turbulateurs tout en formant des points de jonction sécables entre le turbulateur et la feuille,
• pliage ou emboutissage de la feuille,
• rupture des points de jonction sécables de manière à séparer les turbulateurs de la feuille.

The invention further relates to a method for manufacturing turbulators according to the invention, from a sheet or sheet of corrosion-resistant material and temperature, for example refractory stainless steel, characterized in that it comprises the following steps:

• cutting the sheet so as to define the contours of the turbulators while forming breakable junction points between the turbulator and the sheet,
• folding or stamping the sheet,
• rupture of the breakable junction points so as to separate the turbulators from the sheet.

Advantageously, the turbulators are cut so that they are arranged head to tail.

This characteristic makes it possible to limit the falls of the steel sheet or sheet, in particular in the case where the maximum width of the lamellae varies progressively.

• Figure 1 est une vue schématique d'une chaudière à tubes de fumées de l'art antérieur ;
• Figure 2 est une vue en coupe médiane d'un tube dans lequel est inséré un turbulateur selon l'invention ;
• Figure 3 est une vue de côté du turbulateur,
• Figure 4 est une vue en coupe A-A du tube et du turbulateur ;
• Figure 5 est une vue de dessus du tube et du turbulateur.

In any case, the invention will be better understood from the description which follows, with reference to the appended schematic drawing showing, by way of non-limiting example, an embodiment of this turbulator.

• Figure 1 is a schematic view of a flue gas boiler of the prior art;
• Figure 2 is a view in median section of a tube in which is inserted a turbulator according to the invention;
• Figure 3 is a side view of the turbulator,
• Figure 4 is a sectional view AA of the tube and the turbulator;
• Figure 5 is a top view of the tube and the turbulator.

The Figures 2 and 3 represent a turbulator according to the invention. In particular, the figure 2 represents the turbulator in position in a boiler tube.

A turbulator 10 shown in the drawing consists of an elongated element in the form of a blade comprising a succession of lamellae contiguous 11 constituting a zig-zag shape, that is to say extending obliquely and alternately in two opposite directions so as to define a periodic pattern.

The turbulator 10 is inserted into a corresponding tube 4 by a first end 12 and comes to rest, at a second end 13, against the upper edge 14 of the tube 4 by means of a transverse support bar 15 of length greater than the diameter of the tube 4.

Only 3 slides were represented at Figures 2 and 3 , although the turbulator 10 may comprise a larger number of lamellae 11. For reasons of legibility of the drawing, only the lamellae located respectively in the upper part 11a, median 11b and bottom 11c of the tube have been shown.

Each lamella 11 has rounded convex edges 16. The maximum widths La, Lb, Lc of three successive lamellae increase in the direction F of flue gas flow. Thus, the slat located in the upper part 11a is narrower than that in the lower part 11b.

For example, for a tube 4 of internal diameter equal to 33 mm, the maximum width of the strip located in the upper part 11a of the tube 4 is of the order of 20 mm. Similarly, the maximum width of the strip located in the lower part 11c of the tube 4 is of the order of 30 mm.

For a tube 4 with a length of about 600 mm, the turbulator comprises between 10 and 20 lamellae according to the folding angle α.

The turbulator 10 is made by folding from a refractory stainless steel element, so as to obtain substantially planar lamellae 11 whose folds 17 are arranged perpendicularly to the longitudinal axis A of the turbulator 10 and whose bending angles α are constant.

The angle α formed between two successive lamellae 11 is between 90 and 135 °, preferably of the order of 120 °.

The angle α and the dimension of the lamellae 11 are adapted so that the turbulator 10 comes to be positioned, via the fold zones 17 situated between the lamellae, against the inside wall 18 of the tube 4.

Each edge 19 of the fold zones 17 thus comes into contact with the inner wall 18 of the tube 4, so that the turbulator 10 is correctly positioned inside the tube 4, as shown in FIGS. Figures 4 and 5 .

The steps of the method of manufacturing the turbulator 10 are detailed below.

A refractory stainless steel sheet or sheet is used, on which the contour of several turbulators is laser cut. More precisely, an incomplete cut is made so as to form breakable junction points. The turbulators are arranged head to tail so as to reduce the falls after cutting. A folding or stamping operation then makes it possible to form the folds at a predetermined angle. Finally, each turbulator is detached from the sheet by cutting the corresponding junction points.

Of course, the cutting can be performed by any known means and the turbulators may not be arranged head to tail.

The turbulator makes it possible to obtain considerably increased results compared to the turbulators of the prior art. These results are presented below with the help of examples illustrating several different configurations of turbulators.

For each example, unless otherwise indicated, the flue gas temperature in the upper part of the tube is of the order of 1000 ° C, the turbulator has 20 lamellae, the internal diameter of the tube is equal to 33 mm and the bending angle is equal to 90 °.

The parameters for evaluating the efficiency of the turbulator are the flue gas temperature at the outlet, that is to say at the bottom of the tube and the pressure drop generated.

For a turbulator with a constant rectangular section in plan view, corresponding to the turbulators of the type of those described in the documents US 1,632,888 and US 4,412,558 with a constant width of the lamellae of the order of 22 mm, a high flue gas outlet temperature of the order of 116.degree. C. and a pressure drop of around 50 Pa are obtained.

Under similar conditions, the turbulator described in the document US 2,067,133 allows to obtain a lower pressure drop, of the order of 19 Pa but with a very high smoke outlet temperature, of the order of 130.9 ° C.

For a turbulator according to the invention comprising rounded edges as described above, with lamellae of identical cross section, whatever their position in the tube, each lamella having a median zone with a maximum width of 29 mm and a minimum width at folds of 20.6 mm, a fume outlet temperature of the order of 84 ° C and a pressure drop of about 186 Pa are obtained.

As seen previously, it can be seen that a section of rounded shape makes it possible to increase the heat exchanges and thus to reduce the temperature of the fumes. However, this improvement of the efficiency of the boiler is achieved to the detriment of a significant increase in pressure losses.

• largeur maximale de la lamelle située en partie haute du tube : 24,7 mm,
• largeur maximale de la lamelle située en partie basse du tube : 30,6 mm,

on obtient une température de sortie des fumées de l'ordre de 86 °C et une perte de charge de l'ordre de 154 Pa.For a turbulator according to the invention, comprising lamellae of rounded section and whose maximum width varies progressively according to the position of the corresponding lamella in the tube, with the following characteristics:

• maximum width of the strip at the top of the tube: 24.7 mm,
• maximum width of the strip at the bottom of the tube: 30.6 mm,

a flue outlet temperature of the order of 86 ° C. and a pressure drop of about 154 Pa are obtained.

Note that, in comparison with the previous example, the progressivity of the size of the slats can significantly reduce the pressure drop while having little effect on the flue gas outlet temperature, that is to say on the performance of the turbulator.

If, on the basis of the characteristics of the preceding example, a more open bending angle of, for example, 115 ° is achieved, it is possible to reduce the number of sipes, namely 12 sipes in this case, while reducing the loss. load without significantly increasing the flue gas outlet temperature.

This gives a fume outlet temperature of the order of 87 ° C and a pressure drop of the order of 97 Pa.

As goes without saying, the invention is not limited to the embodiments of this set, described above as examples, but it encompasses all the variants as defined by the claims. In particular, the turbulator can be used for flue gas boilers in which the tubes are not arranged vertically.

Claims (10)

1. A turbulator (10), in particular for a boiler (1) with smoke pipes (4) in which the smoke circulates in each pipe from one end to the other, the turbulator being designed to be arranged in a pipe and being made up of a blade-shaped elongated element including a series of adjacent strips (11a, 11b, 11c) and having a zigzag shape, characterized in that the strips (11a, 11b, 11c) include a middle area with a larger width (La, Lb, Lc) than their ends and having rounded convex edges (16).
2. The turbulator (10) according to claim 1, characterized in that the respective widths (La, Lb, Lc) of the middle area of two successive strips (11a, 11 b, 11 c) increase in the direction of circulation of the smoke.
3. The turbulator (10) according to one of claims 1 and 2, characterized in that the strips (11 a, 11 b, 11 c) are substantially planar.
4. The turbulator (10) according to one of claims 1 to 3, characterized in that the connecting areas (17) between two successive strips (11 a, 11 b, 11 c) are arranged perpendicular to the longitudinal direction (A) of the turbulator (10).
5. The turbulator (10) according to one of claims 1 to 4, characterized in that the angle (a) formed between two successive strips (11a, 11 b, 11 c) is comprised between 90 and 135°, preferably approximately 120°.
6. The turbulator (10) according to one of claims 2 to 5, characterized in that the strip of the turbulator (10) situated upstream (11a) in the direction of circulation of the smoke (F) has a maximum width (La) comprised between 55 and 85% of the inner diameter of the pipe (4).
7. The turbulator (10) according to one of claims 2 to 6, characterized in that the strip of the turbulator (10) situated downstream (11c) in the direction of circulation of the smoke (F) has a maximum width (Lc) comprised between 80 and 95% of the inner diameter of the pipe (4).
8. A boiler (1) with smoke pipes (4), characterized in that it includes at least one turbulator (10) according to one of claims 1 to 7, inserted into at least one smoke pipe (4).
9. A method for manufacturing turbulators according to one of claims 1 to 7, from a sheet or sheet metal of a material withstanding corrosion and temperature, for example refractory stainless steel, characterized in that it includes the following steps:

   - cutting the sheet so as to define the contours of the turbulators while forming breakable junction points between the turbulator and the sheet,

   - folding or stamping the sheet,

   - breaking the breakable junction points so as to separate the turbulators from the sheet.
10. The method for manufacturing turbulators according to claim 9, characterized in that the turbulators are cut such that they are arranged head-to-tail.

Images